1. Heat the oil in the saucepan, then cook the leeks over a medium high heat for about 3 minutes or until soft.
2. Add the chicken, stock and wine.
3. Simmer uncovered for 45 minutes or until tender.
4. Add the mushrooms and parsley and cook for a further 5 minutes.
5. Add the salt and pepper.
6. Mix the cornflour with the water and mix to a smooth paste.
7. Add to the Saucepan and stir until it boils and thickens.
8. Leave to cool.
9. Pre-heat the oven to 180C/350F or gas mark 4.
10. Roll the shortcrust pastry onto a floured surface to about 1/8 inch (3mm)
11. Line the ovenproof dish with the pastry.
12. Spoon the mixture into the ovenproof dish.
13. Roll the puff pastry onto a floured surface to about 1/8 inch (3mm)
14. Place the pastry onto the ovenproof dish, covering all the meat.
15. Brush the pastry with the egg, and make a slit in the top.
16. Bake for 20 minutes or until brown.

Serve the pie with broccoli, carrots and new potatoes, for a nice varied meal.